Combination rod and ball grinding mill



llg- 11, 1964 E. J. KLovERs COMBINATION Ron AND BALL GRINDING MILL Filed Oct. 31, 1961 United States Patent C) 3,lt4,212 CMKSINAHUN RGD AND BALL GRENEING Milli.. Ervin l. Klovers, ltdilwaukee, Wis., assigner to Allis- Chalrners Manufacturing Company, Milwaukee, Wis. lFiierl filet. fill, wel, Ser. No. 148,933 S Elanna. (Cl. Zell- 76) This invention relates to grinding mills and in particular to multiple compartment mills that are utilized to perform relatively coarse and relatively line stages of Wet grinding in a single machine.

It may at times be considered advantageous to combine the coarse grinding action of rods and the finer grinding action of balls, each in their own compartment within a single machine. A compartment containing rods may be separated from a compartment containing balls by such as a perforated bulkhead in the middle of the machine. Such machines have not, however, achieved great popularity in the past because of the tendency of the rods to break. In order that material be progressively reduced in size, flow through such a multiple compartment mill is from the coarse grinding rod compartment end toward the ball compartment end. Thus rods (which tend to wear to tapered ends) are carried toward the perforated bulkhead and eventually some may plug the perforations. Pieces are broken from ends of rods near the bulkhead and pieces in other portions of the mill tend to be carried from the material inlet end of the mill toward the perforated bulkhead separating the two compartments of the mill. Thus the relatively short pieces broken from the initially longer rods, tend to accumulate at the bulkhead where they interfere with the desired flow of raw material through the grinding mill and interfere with the desired action of the rods. Grinding efliciency will drop because pieces Will find their way between the end portions of Whole rods. Rod breakage will increase because end portions of tumbling whole rods strike pieces, thus making more pieces. Eventually a suicient number of such rod pieces accumulate so that it becomes necessary that they be removed from the mill. With machines of the prior art, this requires a major shutdown of the grinding mill and considerable inconvenience in the gaining of admission to the midportion of the mill where these pieces have accumulated.

An object of the present invention is to provide a new and improved double compartment grinding mill with rod and ball grinding sections and a trap for pieces of broken rods to minimize interference by such pieces with good grinding action and the How of material through the mill. Another object is to provide for easy and convenient removal of such accumulated rod pieces from the charge of material being ground.

And still another object is to accomplish the foregoing objects without resorting to intermediate discharge, screening and re-entry of a great portion of material along a material ilow circuit thus partly external to the mill, which is an approach that in the past led to more complicated grinding mills.

In a preferred embodiment of the present invention, a rod grinding compartment is provided on the inlet end of the mill and a ball grinding compartment on the discharge end of the mill. These two compartments are separated by a perforated bulkhead. An annular wall, usually made up of imperforate sectors, is spaced axially away from the perforated bulkhead and on the inlet or rod grinding side of the perforated bulkhead. The diameter of the central openingrdefined by the annular wall may be between about 1/6 to 1/a of inner diameter of the mill. Materials partially ground in the coarse grinding section (about 25 to 45 percent of the space in this section being filled with rods) spill over the circular edge i forate.

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of the annular wall into the chamber defined between this wall and the perforated bulkhead. Pieces of broken grinding rods will be carried with the material into this chamber. This material in the chamber will pass through the perforated bulkhead and into the ball grinding compartment. Broken pieces of grinding rod will be trapped in the chamber between the bulkhead and the annular wall. A plurality of radially extending access ports may be arranged around the periphery of the chamber to provide convenient access for removing the pieces of broken rods when rotation of the mill is stopped, regardless of the position of the mill upon stopping.

Removal of broken pieces of rod is facilitated by the annular wall which not only serves to dene the chamber for trapping small pieces of broken rod, but also serves as a barrier to whole rods which prevents their ends (worn to a taper) poking into the perforations in the bulkhead and also prevents the intrusion of whole rods into the space where the pieces accumulate. Thus whole rods do not interfere with or block flow of material through the mill or the discharge of pieces of rod when one of the downwardly pointed ports is opened. By thus providing for quick and easy removal of broken rods, time for performing such tasks is minimized.

Other features and objects of the invention that have been attained will appear from the following more detailed description of the invention with reference to the accompanying drawing, in which:

FlG. 1 shows a view in vertical section of a multistage rotary grinding mill according to the present invention; and

FIG. 2 is a partial view of a transverse vertical section taken along line II-ll in FIG. 1 and in the direction indicated by the arrows.

The multistage grinding mill disclosed in the drawing comprises in general a rotary cylindrical casing 1 illustrated as having uniform or substantially uniform diameter throughout its length, the casing being provided with feed and discharge end heads 2, 3, respectively. The casing ll is divided into a pair of grinding chambers 4 and 5 in a manner and by structure that will be described in detail later. The chamber 4 on the inlet end of the casing l is provided with a plurality of rods 6 that provide for relatively coarse grinding in the chamber 4. The chamber' 5 is provided with a plurality of balls 7 for relatively fine grinding of material in the chamber 5. The mill is rotatably mounted in suitable end bearings which carry feed and discharge trunnions il and 12, respectively. Rotary motion about its horizontal central axis is imparted to the mill by means of power applied to a driving gear lli secured around the inlet end of the casing I1. The feed end of the mill is provided with a feeder 15 for introducing the material which is to be reduced into the inlet end of the coarse grinding chamber t through the feed trunnion 11.

The discharge end of chamber 5 is provided with a perforated plate ll which is spaced from the end head` 3. Located within the space between plate 19 and the end head 3 is a series of elevating vanes 2.0. The inner exrtremities of the elevating vanes 2lb are located close to a central discharge cone 2l, the apex of which is directed toward the discharge trunnion 12.

The arrangement shown for dividing the: casing l into the two grinding compartments d and 5, includes an arrangement of parts novel to the present invention that.

will now be described. i A circular bulkhead 22 is secured around its periphery to the inner surface of casing l.. The bulkhead 22 is perforated with openings Z3 at least throughout an annular area radially outward of a centrally located portion 24 which may be perforated or imper- An annular wall Z5 (made up of imperforate J sections h, see FIG. 2)is similarly secured about its periphery to the inner surface of the casing 1. The annular wall 25 is axially spaced from the bulkhead 22 in the axial direction toward the inlet end of the mill. A chamber 26 is thereby defined between the bulkhead 22 and the annular wall 25. Both the rod chamber 4 and the ball chamber 5 are of considerably greater axial length than the intermediate chamber 26. No grinding media is deliberately placed in the chamber 26. However, its function to trap and collect broken rod pieces will appear as the description of the invention proceeds.

Access to the chamber 26 may be provided by a series of radial ports liti that are spaced circumferentially around casing 1 and each of which open into the chamber 26. A cap 31 may be provided to close the ends of each of the ports 3i) in any desired manner. As shown in the drawing, selectively operable means to open and close port comprise a cap 31 and a liner 33. The liner 33 may be fitted within the ports Sli to project radially outward of casing 1. This liner 33 may be threaded on its external surface to engage cooperating threads in the cap 31.

Replaceable liners such as 36, 37 may be provided for protecting such as the feed end head 2, the cylindrical casing 1 and the annular wall 35.

In the `operation of the mill disclosed in the drawing, material is admitted to the coarse grinding charnber 4 by the feeder 15. To reduce the size of larger particles of the material, rotation is imparted to the shell 1 by the gear 13. The material requiring reduction is given its initial reduction in size during passage through the coarse grinding chamber 4 by the tumbling and rubbing action of `the rods 6. The material within the chamber 4 in addition to being reduced in size, will move axially (by displacement) through the chamber from the feed end 2 toward the annular Wall 25. The coarse ground material will spill over the edge 25a of the annular Wall and fall into the chamber 26. From the chamber 26 the coarse ground material will pass through the openings 23 in bulkhead 22 and pass into the line grinding chamber 5. Within the line grinding chamber 5 the material will be further reduced in size. All material will pass through the perforated plate 19 and this material will be picked up by the elevating vanes 20 which drop the material upon the cone 21. As the material falls downwardly upon the cone 21, it also slides axially toward the apex of the cone from which it falls into the discharge trunnion 12, then into a chamber and by gravity down through a discharge spout 42. Material discharged from the spout 42 may be carried away in any desired and conventional manner.

The chamber 26 which according to the present invention is placed between the coarse rod grinding section 4 and the fine grinding section 5, not only collects the coarse ground material for transfer to the fine grinding section 5, but also collects pieces or broken rod from the coarse grinding section 4. Eventually, of course, the pieces of broken rod may accumulate to a sufiicient quantity that these pieces themselves interfere with the desired flow of material through the mill. At such times the mill may be stopped and one or more downwardly pointed caps 31 removed to open ports 30 and discharge the pieces of broken rods that have accumulated in chamber 26. The small amount of coarse ground material that will come out with the pieces of rod, may, for example, be separated from the rod pieces and reintroduced to feeder 15. Since annular wall 25 acts as a barrier to whole rods, such rods cannot interfere with iiow through the mill and/or the discharge from chamber 26 and the pieces in chamber 26 can be removed quickly and with a minimum lost shutdown time for the mill.

From the foregoing it can be seen that the described construction accomplishes the objects of the invention. However, modifications and equivalents as can be exi pected to occur to those skilled in the art are intended to be included within the scope of this invention and thus the invention is intended to be limited only by the scope of the claims appended hereto.

Having now particularly described and ascertained the nature of my said invention and the manner in which it is to be performed, I declare that what l claim is:

1. A grinding mill comprising:

a casing supported for rotation about a central axis;

inlet means connected to one end of said casing for delivering materials to be ground to the interior of Y said casing and discharge means connected to other end of said casing;

a perforated bulkhead within said casing intermediate 'the ends thereof and transverse thereto;

a charge of fine grinding media within said casing on the side of said bulkhead facing said discharge means;

a charge of coarse grinding media within said casing on the side of said bulkhead facing said inlet means; an annular wall within said casing and transverse thereto, said annular wall being axially spaced away from the side of said perforated bulkhead facing said inlet means, said wall and said bulkhead defining therebetween an intermediate chamber between an inlet end chamber and a discharge end chamber within said casing, said fine grinding media being confined to said discharge end chamber by said bulkhead and said coarse grinding media being confined to said feed end portion by said annular wall which provides a barrier thereto, Said annular wall also defining a central opening for coarse ground material and pieces of broken coarse grinding media to flow from said inlet end chamber into said intermediate chamber with the coarse ground material flowing from said intermediate chamber into said discharge end chamber through said perforated bulkhead for fur-ther grinding by said fine grinding media but said pieces of broken coarse grinding media being trapped within said intermediate chamber.

2. A grinding mill comprising:

a cylindrical casing supported for rotation about its central axis and with its central axis in a general horizontal position;

inlet means connected to one end of said casing for delivering materials to be ground to the interior of said casing and discharge means connected to other end of said casing;

circular perforated bulkhead within said casing intermediate the ends thereof and transverse thereto;

a charge of grinding balls within said casing on the Side of said bulkhead facing said discharge means;

a charge of grinding rods within said casing on the side of said bulkhead facing said inlet means;

an annular wall within said casing and transverse thereto, said annular wall being axially spaced away from the side of said perforated bulkhead facing said inlet means, said wall and said bulkhead defining therebetween an intermediate chamber between an inlet `end chamber and a discharge end chamber within said casing, said balls being confined to said discharge end chamber by said bulkhead and said rods being confined to said feed end portion by said annular wall which provides a barrier thereto, said annular wall also defining a central opening for rod ground material and pieces of broken rod to flow Y from said inlet end chamber into said intermediate chamber with the rod ground material owing from said intermediate chamber into said discharge end chamber for further grinding by said balls but said pieces of broken rod being trapped within said intermediate chamber.

. A grinding mill comprising:

cylindrical casing supported for rotation about its central axis and with its central axis in a generally horizontal position;

inlet means connected to one end of said casing for delivering materials to be ground to the interior of said casing and discharge means connected to other end of said casing;

a circular bulkhead within said casing intermediate the ends thereof and transverse thereto, said bulkhead being perforated to define a plurality of axially eX- tending holes located throughout an annular area around a central area;

a charge of grinding balls within said casing on the side of said bulkhead facing said discharge means;

a charge of grinding rods within said casing on the side of said bulkhead facing said inlet means;

an annular wall made up of imperforate sectors within said casing and transverse thereto, said annular wall being axially spaced away from the side of said perforated bulkhead facing said inlet means, said wall and said bulkhead defining therebetween an intermediate chamber between an inlet end chamber and a discharge end chamber within said casing, said balls being confined to said discharge end chamber by said bulkhead and said rods being confined to said feed end portion by said annular wall which provides a barrier thereto, said annular wall also defining a central opening for rod ground material and pieces of broken rod to flow from said inlet end chamber into said intermediate chamber, said holes in said bulkhead being of smaller diameter than the diameter of said rods whereby rod ground material flows from said intermediate chamber into said discharge end chamber for further grinding by said balls but said pieces of broken rod are trapped within said intermediate chamber.

4. A grinding mill comprising:

a cylindrical casing supported for rotation about its central axis and with its central axis in a generally horizontal position;

inlet means connected to one end of said casing for delivering materials too be ground to the interior of said casing and discharge means connected to other end of said casing;

a circular bulkhead within said casing intermediate the ends thereof and transverse thereto, said bulkhead being perforated to define a plurality of axially extending holes located throughout an annular area around a central area;

a charge of grinding balls within said casing on the side of said bulkhead facing said discharge means;

a charge of grinding rods within said casing on the side of said bulkhead facing said inlet means;

an annular wall made up of imperforate sectors within said casing and transverse thereto, said annular wall being axially spaced away from the side of said perforated bulkhead facing said inlet means, said wall and said bulkhead dening therebetween an intermediate chamber between an inlet end chamber and a discharge end chamber within said casing, said balls being confined to said discharge end chamber by said bulkhead and said rods being confined to said feed end portion by said annular wall which provides a barrier thereto, said annular wall also defining a central opening for rod ground material and pieces of broken rod to flow from said inlet end chamber into said intermediate chamber, said holes in said bulkhead being of Smaller diameter than the diameter of said rods whereby rod ground material flows from said intermediate chamber into said discharge end chamber for further grinding by said balls but said pieces of broken rod are trapped within said intermediate chamber;

said casing defining a plurality of radial ports communicating with said intermediate chamber, each of said ports being fitted with a cylindrical liner projecting radially outward of said casing; and

a cap removably fitted to the radially outer end of each liner whereby at least one of said caps can be removed from one of said liners pointed generally downward to discharge pieces of broken rod from said intermediate chamber.

5. A grinding mill comprising:

a casing supported for rotation about a central axis;

inlet means connected to one end of said casing for delivering materials to be ground to the interior of said casing and discharge means connected to other end of said casing;

a perforated bulkhead within said casing intermediate the ends thereof and transverse thereto;

a charge of fine grinding meda within said casing on the side of said bulkhead facing said discharge means;

a charge of coarse grinding media within said casing on the side of said bulkhead facing said inlet means; an annular wall within said casing and transverse thereto, said annular wall being axially spaced away from the side of said perforated bulkhead facing said inlet means, said wall and said bulkhead defining therebetween an intermediate chamber between an inlet end chamber and a discharge end chamber within said casing, said fine grinding media being conned to said discharge end chamber by said bulkhead and said coarse grinding media being confined to said feed end portion by said annular wall which provides a barrier thereto, said annular wall also defining a central opening for coarse ground material and pieces of broken coarse grinding media to flow from said inlet end chamber into said intermediate chamber with the coarse ground material liowing from said intermediate chamber into said discharge end chamber through said perforated bulkhead for further grinding by said fine grinding media but said pieces of broken coarse grinding media being trapped within said intermediate chamber;

said casing defining a port communicating with said intermediate chamber; and means connected to said port that is selectively operable to open and close said port whereby pieces of broken coarse grinding media are discharged from said intermediate chamber upon opening said selectively operable means.

6. A grinding mill comprising:

a cylindrical casing supported for rotation about its central axis and with its central axis in a generally horizontal position;

inlet means connected to one end of said casing for delivering materials to be ground to the interior of said casing and discharge means connected to other end of said casing;

a circular perforated bulkhead within said casing intermediate the ends thereof and transverse thereto;

a charge of grinding balls within said casing on the side of said bulkhead facing said discharge means;

a charge of grinding rods within said casing on the side of said bulkhead facing said inlet means;

an annular wall within said casing and transverse thereto, said annular wall being axially spaced away from the side of said perforated bulkhead facing said inlet means, said wall and said bulkhead deining therebetween an intermediate chamber between an inlet end chamber and a discharge end chamber within said casing, said balls being confined to said discharge end chamber by said bulkhead and said rods being confined to said feed end portion by said annular Wall which provides a barrier thereto, said annular wall also defining a central opening for rod ground material and pieces of broken rod to flow from said inlet end chamber into said intermediate chamber with the rod ground material flowing from said intermediate chamber into said discharge end chamber for further grinding by said balls but said pieces of broken rod being trapped within said intermediate chamber;

said casing dening a port communicating with said intermediate chamber;

and selectively operable means connected to said port 7. A grinding mill comprising: 10 a casing supported for rotation about a central axis; inlet means connected to one end of said casing for delivering materials to be ground to the interior of said casing and discharge means connected to other end of said casing;

a perforated bulkhead within said casing intermediate the ends thereof and transverse thereto;

a charge of ne grinding media within said casing on the side of said bulkhead facing said discharge means;

` a charge of coarse grinding media within said casing on the side of said bulkhead facing said inlet means;

an annular wall within said casing and transverse thereto, said annular wall dening a central opening of a diameter between about 1/6 to 1/3 of the inner diameter of said casing, said annular wall being axially spaced away from the side of said perforated bulkhead facing said inlet means, said wall and said bulkhead dening therebetween an intermediate chamber between an inlet end chamber and a discharge end chamber within said casing, said i'ine grinding media 30 being conned to said discharge end chamber by said bulkhead and said coarse grinding media being conned to said feed end portion by said annular Wall which provides a barrier thereto, said annular wall also defining a central opening for coarse ground material and pieces of broken coarse grinding media to flow from said inlet end chamber into said intermediate chamber with the coarse ground material owing from said intermediate chamber into said discharge end chamber through said perforated bulkhead for further grinding by said tine grinding media but said pieces of broken coarse grinding media being trapped within said intermediate chamber.

8. A grinding mill comprising:

a cylindrical casing supported for rotation about its central axis and with its central axis in a generally horizontal position;

' inlet means connected to one end of said casing for delivering materials to be ground to the interior of said casing and discharge means connected to other end of said casing; n

a circular perforated bulkhead within said casing intermediate the ends thereof and transverse thereto;

a charge of grinding balls within said casing on the side of said bulkhead facing said discharge means;

a charge of grinding rods within said casing on the side of said bulkhead facing said inlet means, said charge comprising a quantity of rods filling about 25 to 45 percent of the space on said inlet side of said bulkhead;

an annular wall within said casing and transverse thereto, said annular wall defining a central opening of a diameter of about 1/6 to 1/3 of the inner diameter of said casing, said annular wall being axially spaced away from the side of said perforated bulkhead facing said inlet means, said wall and said bulkhead dening therebetween an intermediate chamber between an inlet end chamber and a discharge end chamber Within said casing, said balls being confined to said discharge end chamber by said bulkhead and said rods being coniined to said feed end portion by said annular Wall which provides a barrier thereto, said annular wall also dening a central opening for rod ground material and pieces of broken rod to ilow from said inlet end chamber into said intermediate chamber with the rod ground material flowing from said intermediate chamber into said discharge end chamber for further grinding by said balls but said pieces of broken rod being trapped within said intermediate chamber.

References Cited in the ile of this patent UNITED STATES PATENTS 

1. A GRINDING MILL COMPRISING: A CASING SUPPORTED FOR ROTATION ABOUT A CENTRAL AXIS; INLET MEANS CONNECTED TO ONE END OF SAID CASING FOR DELIVERING MATERIALS TO BE GROUND TO THE INTERIOR OF SAID CASING AND DISCHARGE MEANS CONNECTED TO OTHER END OF SAID CASING; A PERFORATED BULKHEAD WITHIN SAID CASING INTERMEDIATE THE ENDS THEREOF AND TRANSVERSE THERETO; A CHARGE OF FINE GRINDING MEDIA WITHIN SAID CASING ON THE SIDE OF SAID BULKHEAD FACING SAID DISCHARGE MEANS; A CHARGE OF COARSE GRINDING MEDIA WITHIN SAID CASING ON THE SIDE OF SAID BULKHEAD FACING SAID INLET MEANS; AN ANNULAR WALL WITHIN SAID CASING AND TRANSVERSE THERETO, SAID ANNULAR WALL BEING AXIALLY SPACED AWAY FROM THE SIDE OF SAID PERFORATED BULKHEAD FACING SAID INLET MEANS, SAID WALL AND SAID BULKHEAD DEFINING THEREBETWEEN AN INTERMEDIATE CHAMBER BETWEEN AN INLET END CHAMBER AND A DISCHARGE END CHAMBER WITHIN SAID CASING, SAID FINE GRINDING MEDIA BEING CONFINED TO SAID DISCHARGE END CHAMBER BY SAID BULKHEAD AND SAID COARSE GRINDING MEDIA BEING CONFINED TO SAID FEED END PORTION BY SAID ANNULAR WALL WHICH PROVIDES A BARRIER THERETO, SAID ANNULAR WALL ALSO DEFINING A CENTRAL OPENING FOR COARSE GROUND MATERIAL AND PIECES OF BROKEN COARSE GRINDING MEDIA TO FLOW FROM SAID INLET END CHAMBER INTO SAID INTERMEDIATE CHAMBER WITH THE COARSE GROUND MATERIAL FLOWING FROM SAID INTERMEDIATE CHAMBER INTO SAID DISCHARGE END CHAMBER THROUGH SAID PERFORATED BULKHEAD FOR FURTHER GRINDING BY SAID FINE GRINDING MEDIA BUT SAID PIECES OF BROKEN COARSE GRINDING MEDIA BEING TRAPPED WITHIN SAID INTERMEDIATE CHAMBER. 